Question

A parallel beam fo white is incident normally on a water film $1.0\times {10}^{-4}$ cm thick. Find the wavelength in the visible range (400 nm - 700 nm) Which are strongly transmitted by the film. Refractive index of water = 1.33.

Answer 1

For strong transmission,
$2\mu d=nm\Rightarrow l=2\frac{\mu d}{n}$
Given that: $\mu =1.33,d=1\times {10}^{-4}cm=1\times {10}^{-6}m\Rightarrow \lambda =\frac{2\times 1.33\times 1\times {10}^{-6}}{n}=\frac{2660\times {10}^{-9}}{n}m$
When, $n=4,{\lambda }_1=665nmn=5,{\lambda }_2=532nmn=6,{\lambda }_3=443nm$